Polyester resins have been prepared in the past by reacting such carboxylic acids as diglycolic acid with a dihydric alcohol such as a glycol but these polyester resins of the prior art were of comparatively low molecular weight such as about 3,000 or 4,000 molecular weight and had an inherent viscosity of about 0.25. These low molecular weight polyesters of diglycolic acid and glycols were not capable of forming a self-supporting film and were suggested for use as a propellant plasticizer among other things. If one could produce a polyester of diglycolic acid and a glycol of sufficiently high molecular weight so as to provide a polymeric material which possesses self-supporting film forming properties, a film could be produced therefrom which films could provide a delivery system for a predetermined dosage of a drug by controlled continuous administration. Such a film would be a biodegradable film which would be hydrolyzable and which could be implanted or otherwise deposited in the body of a living animal which would release the dosage of a drug and when the function as a dosage release device had served its purpose the hydrolyzable biodegradable film would be substantially completely absorbed in varying periods of time.